Yes it is. This downs its special attack and raises it's speed. Abra and it's evolutions have two good natures: Modest and Timid. Modest raises it's special attack, but lowers it's attack stat. This isn't a problem since abra and it's evolutions are special sweepers and have a low attack stat already. Timid raises its speed but lowers it's attack stat. Again this isn't a problem since it doesn't lower it's awesome special attack but it's already embarrassing attack stat that would not even be used anyway. Keep in mind, never, ever use a jolly abra, kadabra or alakazam .
Hope this helped